1. Field of the Invention
The present invention relates to a common package, and particularly, to a common network interface package applicable to a switching system.
2. Description of the Related Art
A switching system generally consists of four kinds of apparatuses, i.e., 1) apparatuses for making connections between subscribers, between trunks, or between subscribers and trunks, 2) channel apparatuses for receiving subscriber lines and trunk units and controlling and testing channels, 3) central processing apparatuses for analyzing data entering the switching system and issuing instructions to the channel apparatuses and I/O apparatuses, and 4) the I/O apparatuses for sending and receiving data to and from the central processing apparatuses.
FIG. 1 shows a conventional switching system.
Subscriber terminals 11 are connected to subscriber lines, which are received by subscriber circuits (SLCs) 12 of the switching system. Signals from the subscriber circuits 12 are multiplexed by subscriber concentrators (SLCCs) incorporated in a network interface (NW-INF1) 13. More precisely, the network interface 13 converts signals from subscribers into time slots in highway signals.
The highway signals are multiplexed by a network unit (NW) 14 into a higher highway signal, which is transferred to a switch (SW) 19. A line processor (LPR) 15 processes scan data (SCN) indicating the ON/OFF-hook states of subscriber terminals and signal data (SD) from higher devices. For local connections, the line processor 15 carries out switching operations within the network unit 14. The line processor 15 also controls and tests channels.
Signals from trunk circuits (TRKS) 16 are multiplexed by trunk concentrators (ATCs) incorporated in a network interface (NW-INF2) 17. More precisely, the network interface 17 converts trunk signals into time slots in highway signals, which are multiplexed by a network unit (NW) 18 into a higher highway signal. The higher highway signal is transferred to the switch 19.
According to instructions from a central processing apparatus (CC) 20, the switch 19 exchanges time slots in higher highway signals and realizes connections among the subscribers and trunks through the network units 14 and. 18. An I/O apparatus 21 sends and receives data for system management and maintenance to and from the central processing apparatus 20.
FIGS. 2A and 2B show the structures of a time slot and highway signal transferred between the network interface 13 and the network unit 14.
The time slot (TS) of FIG. 2A is for voice data and consists of eight bits, and the highway signal of FIG. 2B consists of 8-bit time slots and includes housekeeping data and SD/SCN (signal data/scan) data.
In FIG. 2B, a frame of the highway signal has a frequency of 8 KHz (a period of 125 xcexcs) containing 128 time slots TS0 to TS127. The time slots TS0 to TS3 carry the housekeeping data containing maintenance and management data. The time slots TS64 to TS67 carry the SD/SCN data.
Each frame contains housekeeping data of 32 bits (=8 bitsxc3x974 time slots) and SD/SCN data of 32 bits. In this example, 16 frames form a multiframe having a period of 2 ms (125 xcexcsxc3x9716), and data is updated multiframe by multiframe.
The network interfaces 13 and 17 are connected to the network units 14 and 18 and control the discrete circuits 12 and 16 arranged under the network interfaces 13 and 17. The network interfaces 13 and 17 achieve different functions, and therefore, are composed of different packages.
Each network interface has a shelf on which network interface packages are installed to control the discrete circuits such as the subscriber circuits 12 and trunk circuits 16. These packages are designed exclusively for the discrete circuits, and therefore, have the following problems:
(1) Too Many Kinds of Packages
On the one hand, the network interface packages have each a common interface with respect to the network units 14 and 18. For example, the subscriber concentrators in the network interface 13 and the trunk concentrators in the network interface 17 have each a common interface with respect to the network units 14 and 18.
On the other hand, the packages have different interfaces or LSIs optimized for the subscriber circuits 12 or trunk circuits 16. This is because back wiring boards (BWBs) arranged on the shelves of the network interfaces 13 and 17 for the packages differ from one to another depending on the circuits 12 and 16.
Recent development in multimedia communication has increased the number of discrete circuits. To cope with this, a variety of network interface packages must be prepared. This results in increasing the production, maintenance, and management costs of the packages.
(2) Problems in Highway Interfacing of Packages
A highway signal transferred between the network interface 13 (17) and the network unit 14 (18) employs a format that contains both voice data and control data such as SD/SCN. This format restricts the quantity of the control data to a minimum in the predetermined time slots as shown in FIG. 2B.
Recent development in multimedia communication has produced a variety of control data and has increased the quantity thereof, and these expanding pieces of control data are hardly handled with information provided by the predetermined time slots in the highway signal.
The conventional technique of arranging voice data and control data in the same highway signal is inefficient. For example, one must execute a program each time to monitor every frame in each multiframe of the highway signal at intervals of 125 xcexcs to see if packages have been installed on or removed from a shelf. This deteriorates the overall efficiency of the switching system.
The control data contained in the highway signal is a mixture of different functions. Namely, pieces of the control data are disorderly arranged in the highway signal, and therefore, are inefficiently processed by a microprocessor or software for switching work. This deteriorates the overall efficiency of the switching system.
An object of the present invention is to provide a network interface package to be installed on a shelf of a network interface, having a common structure for lower circuit blocks and a general structure for a network unit, to help reduce the kinds of network interface packages and decrease the production, maintenance, and management costs thereof.
In order to accomplish the object, a first aspect of the present invention provides a common package installed in an apparatus and configurable to serve as a selected one of specific circuits. The common package consists of a programmable device, a memory for storing programs to configure the programmable device, a selector for selecting one of the programs from the memory so that the selected program may so configure the programmable device as to make the common package serve as a specific circuit, and an instruction unit for issuing an instruction to specify the program to be selected by the selector.
A second aspect of the present invention provides a common package installed in an apparatus and configurable to serve as a selected one of specific circuits. The common package consists of a programmable device to be so configured according to a program as to make the common package serve as a specific circuit, a memory for storing the program, an instruction unit for specifying the program, a notify unit for notifying the apparatus of the specified program, and a control unit for receiving the specified program from the apparatus and storing the same in the memory.
The programmable device of any one of the first and second aspects may be an FPGA (field programmable gate array). The memory of the first aspect may consist of nonvolatile memories for storing FPGA controlling programs, respectively. The memory of the second aspect may be a volatile memory.
The instruction unit issues the instruction according to self inventory data provided by a BWB (back wiring board) of the apparatus, or data provided by a manual setting unit installed on the common package. The common package is connected to discrete circuit packages.
The common package may have an interface circuit that includes lines for separately transmitting a data signal and a control signal. Data carried by the control signal is divided into zones each containing similar data.
The arrangements of the present invention may be combined in various ways.